There are many different types of documents and things which are subject to counterfeiting or forgery, and many different techniques and devices have been developed for determining the authenticity of a document or thing. By way of example only, such documents include bank notes, identification papers, passports, drivers licenses, visas, admission tickets and stock certificates. As used herein, the term “secured document” includes any document or thing which is provided with a distinguishing authenticity element (whether printed or not) which can be used to authenticate, identify or classify the document. The term “authentication element” is intended to refer to any “device” which may be printed on, or otherwise attached to, a secured document for the purpose of authenticating the document or for the purpose of determining its value and/or type or any other characteristic. Likewise, “authenticity” is meant to encompass value, type or other characteristic of a secured document as well as the genuineness of the document.
There are machines which automatically examine authentication elements on a multiplicity of secured documents. In one known machine, the secured document is supported on a transparent supporting surface and illuminated from below by a fixed light source. The reflected image is captured by a stationary camera (typically, one or more matrix cameras) and the image evaluated with appropriate software. Such devices have relatively low resolution and, though suitable for reading text within the document, are not suitable for reading a two dimensional bar code or authenticity elements which are based on diffraction or which are hidden steganographically in parts of the image.
Authentication elements are known which operate on principles of light diffraction. With diffraction systems, a light source (typically a laser) illuminates a diffraction element (e.g., a hologram) to produce a diffraction pattern that can be sensed and evaluated to determine authenticity. In known devices of this type, the laser and associated evaluating unit are housed in a hand held unit which can be placed by hand on the authenticity element which can be recognized with the naked eye. Heretofore, such authenticity evaluating units have not been incorporated into machines which are used for automatically examining documents.
Automatic document-examining machines are known which include a flat bed scanner having a slide movable in the Y direction on which an illuminating device and camera are mounted. The camera records the image produced by the illuminated document and evaluates it; however, such flat bed scanners are not suitable for automatically examining authenticity elements which are based on diffraction principals wherein laser illumination is required. Moreover, flatbed scanners are not suitable for identifying special elements on a document which must be illuminated with different sources of illumination.
It is a principal object of the invention to provide a document-examining machine of the type described wherein distinguishing authenticity elements can be examined rapidly and accurately.
A more specific object is to provide a document-examining machine which can be used to automatically examine authenticity elements based on diffraction principals reliably and satisfactorily.